When Otis Cary interrogated Japanese prisoners during World War II, he softened them with gifts of magazines, cigarettes and chocolates. He broke through their reserve with humor. And he spoke to them in flawless Japanese — shocking from a blond-haired American.

Cary spoke like a native because he was one — the son and grandson of New England missionaries in Japan. With missionarylike ardor, he proselytized for the Allied cause, convincing many of the prisoners to cooperate in efforts to end the war and help rebuild Japan as a democracy.

"Prolonged contact with Americans in the prison camps clearly had an impact on many prisoners, and for none more than those influenced by Otis Cary," wrote Ulrich Straus, a former diplomat whose study of Japanese prisoners of war, "The Anguish of Surrender," was published in 2003.

Cary, 84, who died of pneumonia April 14 in Oakland, Calif., played a unique role in U.S.-Japan relations during and after World War II. He was one of the 1,100 Japanese linguists trained by the Navy to serve as interrogators, translators and interpreters after the 1941 attack on Pearl Harbor. For more than four decades after the war, he bridged cultures as a professor of American studies at Doshisha University in Kyoto.

He was, in many respects, more Japanese than American.

"When (Americans) asked him where he came from, he said it pained him to say he was from Massachusetts," said Donald Keene, a Columbia University expert on Japanese literature and longtime friend, who served with Cary during the war.

"To tell a fellow officer 'I came from Japan' was to start a quarrel" in the tense period after Pearl Harbor, Keene explained. But Cary, he noted, "saw Japan as his real home."

Cary's deep understanding of the Japanese enabled him to help POWs overcome their shame at having been captured and their fears of returning home in disgrace. He encouraged them to see themselves as patriots, who gave their all to their country and who now had a duty to support its reconstruction.

He counted among his "converts" POWs who went on to become leaders in the new Japan, including the publisher of a major newspaper and a prominent physician. He also drummed ideas of democracy into members of the imperial family, whom he met on several occasions after Japan's surrender in August 1945.

In 1947, while Japan was still under the Allied occupation, he joined the faculty of Doshisha University as a representative of Amherst College. In 1991 he helped launch Doshisha's graduate school of American studies, the first of its kind in Asia.

For 32 years, he was director of Amherst House, a dormitory where he encouraged Japanese students to dispense with customs that he considered obstacles to modernization. One of his targets was honorific speech, which mandates different degrees of politeness depending on a person's social rank. To put students on an equal footing, Cary just gave them nicknames.

"It was a very innovative idea," said Shigeki Hijino, a former Newsweek correspondent who lived at Amherst House in the early 1960s. Cary's greatest achievement was broadening the minds of the hundreds of students who passed through Amherst House over the years, Hijino said.

"Otis Cary played a key role — I believe an under-recognized one — in helping to ease U.S.-Japan relations, both socially and at the academic level," said Pedro Loureiro, curator of the Pacific Basin Institute at Pomona College, which promotes Asian studies.

Cary was born in Hokkaido on Oct. 20, 1921. He moved to the U.S. after elementary school.

When America entered World War II, he enlisted in the Navy and breezed through its crash course in Japanese. Assigned to a POW camp at Pearl Harbor in early 1943, he became the executive officer of the interrogation section.